Monolithic prioritiser provides low standby for back up

A dual input monolithic power prioritiser for 1.8 to 18V systems has been announced by Linear Technology. The LTC4420 normally powers the load from the higher priority main supply such as a wall adapter or battery, switching to the backup supply—typically a battery or large-value capacitor—during primary brownout or power loss conditions. With up to 18V operating capability, it accommodates a range of power sources such as wall adapters, USB ports, super-capacitors, and stacked batteries with Li-Ion, alkaline or NiMH cells.

By reducing device operating current to 3.6microA and the backup supply’s standby current drain to a low 0.32microA, the prioritiser extends run time in portable battery-operated systems. It does not require the backup supply voltage to be lower than the main supply voltage. When the backup supply voltage is higher than the main supply voltage, a prioritiser does not necessarily draw current from the highest voltage supply. Internal 500mA (min) current-limited switches multiplex from the primary to the backup supply when the primary voltage falls below the adjustable switchover threshold. Break-before-make fast switch control blocks reverse and cross conduction currents while minimising output voltage droop. To reduce quiescent current, the backup supply’s resistive divider is connected to a strobed ground with a duty cycle that is adjustable down to a low 0.0015 per cent, and an optional under-voltage disconnect prevents deeply discharged batteries. A freshness seal mode further lowers standby current to 0.12microA, minimising battery discharge during product storage and shipment. Reversed-battery voltages up to -15V are blocked from propagating to the load.

Operation is over the 0 to 70°C commercial and -40 to +85°C industrial temperature ranges. The prioritiser is offered in thermally enhanced 12pin MSOP and 3.0 x 3.0mm DFN packages. 1

Latest News from Softei

This news story is brought to you by, the specialist site dedicated to delivering information about what’s new in the electronics industry, with daily news updates, new products and industry news. To stay up-to-date, register to receive our weekly newsletters and keep yourself informed on the latest technology news and new products from around the globe. Simply click this link to register here: Softei Registration